The present invention relates to engine control; more specifically, to starting engine cranking control by simply detecting an engine cranking that is caused by an engine starter.
In an earlier vehicle engine, in order to ensure engine start performance by shortening an engine cranking period, fuel injection control, an ignition timing control and an air quantity control inherent for an engine cranking are performed during a cranking period based upon detection of cranking.
The start of the cranking period is detected by inputting a starter switch signal attached to an ignition key cylinder to an engine control unit (ECU). For this detection, a harness from a starter switch to an input terminal of ECU has been used, which increases costs. Therefore, in another earlier technology, the start of engine rotation is judged as when an engine rotation signal is input from a crank angle sensor and then, the engine cranking control is started (Japanese Unexamined Patent Publication No. 2000-257540).
In the above earlier technology, when the engine rotation starts from a condition of no engine rotation, the engine rotation start is detected accurately.
However, when a starter is driven immediately before the engine stops (such as near or at engine stall), because no shift to the engine cranking control is made, the engine is not promptly cranked. Rather, the engine speed must first reach zero, which can be time-consuming.
Further, because the engine will receive an opposite direction force immediately after the engine stops, an engine rotation velocity may be recognized erroneously. On this occasion, the engine is not promptly cranked.
One aspect of the present invention, in view of the foregoing problem, performs a prompt shift to an engine cranking control by accurately detecting a cranking period based upon an engine condition separate from a starter drive signal.
The present invention, in order to achieve the above aspect, involves detecting start of an engine cranking control by estimating that an engine is cranked by a starter on condition that a prior engine cranking control ends, an engine rotation velocity is equal to or less than a limit velocity leading to an engine stall, and a voltage of a starter driving power falls to or below a predetermined low value.
This and other aspects and features of this invention will be understood from the following description with accompanying drawings.